1. Field of the Invention
The present invention relates to a seat suspension device for use in a seat for an automobile or the like.
2. Description of the Prior Art
Conventionally, an automobile is provided with a seat suspension device which is interposed between the seat and the floor surface of the automobile to resiliently support the seat so as to absorb vibrations and shocks produced when the automobile is travelling along bad roads or the like.
As seat suspension devices of this type, conventionally, for example, there are known two suspension devices which are respectively disclosed in Japanese Utility Model Publication No. 151837 of 1984 and Japanese Patent Publication No. 131432 of 1981.
In other words, in the above-mentioned seat support devices, an upper frame is supported such that it can be moved through an X-shaped link in the vertical direction relative to a lower frame, and a coil spring is interposed between the X-shaped link and a frame, whereby the suspension operation thereof is performed by means of the compressing and resiling forces of the coil spring.
However, either of these conventional seat suspension devices employs a coil spring having a large diameter, with the result that the whole seat suspension device is large in weight. Also, when such coil spring is provided within the frame, the frame is great in thickness and, when such coil spring is interposed between the frame and the X-shaped link, there requires a large space between the frames, with the result that the whole seat suspension device becomes large in thickness. Therefore, the above-mentioned prior art seat suspension devices are found disadvantageous in that they are hard to apply to an automobile which is limited in the room space thereof.